Little is known about the patterns of development of children with cerebral palsy which lead to their ultimate functional motor outcome, and as a result rehabilitation goals and gains are often difficult to evaluate. The objective of this program is to describe the natural history of movement development in this population of children. This will help to understand how the "severity" of cerebral palsy might influence how independent a child is able to become. The investigators have been working for ten years to develop a measurement tool to assess the motor function of children with cerebral palsy. This study will build on previous work by using the measure repeatedly over a minimum of three years to document the movement activities of a large group of children of various ages and severities of cerebral palsy. The goal is to create "motor growth curves" similar to the growth charts that are used to follow the height and weight of children as they grow. Along with related work by the investigators on the assessment of "severity" of motor disability, the intent of this study is to provide information on the natural history of motor development in cerebral palsy, and contribute new insights into the planning and evaluation of rehabilitation efforts.